Genetic Heritability Estimates and Personality Flashcards
Minnesota Study of Twins Reared Apart
This landmark study, led by Thomas Bouchard, focused on MZ and DZ twins separated at birth and raised in different environments. The high correlations in personality traits between these MZ twins, even when reared apart, strongly indicate a genetic influence on traits such as neuroticism, with a correlation coefficient of around 0.70 between separated MZ twins.
Genetic Heritability and Personality
Heritability measures the genetic influence on personality traits, typically assessed using twin and adoption studies. Monozygotic (MZ) twins share 100% of their genes, while dizygotic (DZ) twins share 50%, enabling researchers to distinguish genetic and environmental effects.
Twin Studies in the Five-Factor Model (FFM)
The Five-Factor Model of personality (Extraversion, Neuroticism, Agreeableness, Conscientiousness, and Openness) has been widely studied in the context of heritability:
Traits like Extraversion (56%) and Neuroticism (80%) show high heritability. MZ twins have much higher correlation scores compared to DZ twins.
For example, Extraversion showed a heritability estimate of around 56%, with Neuroticism even higher at 80%, suggesting that genetic factors heavily influence these traits.
Heritability Computation and Interpretation
Heritability estimates for twin studies are calculated using the difference in correlations between MZ and DZ twins. For example, a heritability estimate formula h² = 2 (rmz - rdz) calculates the genetic component of a trait by doubling the difference between MZ and DZ twin correlations.
* It’s essential to note that heritability estimates represent average contributions across a population, not individual predictions. A 50% heritability score means that, on average, genetics explain about half of the variation in that trait across a population, not within any specific individual.
Findings from Adoption Studies
Adoption studies support twin study findings by observing that adopted children show more similarity in personality traits with their biological parents than with their adoptive parents, indicating a genetic component.
